1. Field of the Invention
The present invention relates to an apparatus for grinding a semiconductor wafer and, more particularly, to an apparatus which cools a semiconductor wafer using cooling water during grinding.
2. Related Background Art
In a conventional grinding apparatus, a semiconductor wafer is cooled by a continuous flow of cooling water. In this case, the cooling water absorbs heat generate by grinding and is then discharged.
In particular, in a so-called back-grinding process before dicing of a GaAs semiconductor wafer, if this wafer is damaged, the yield of semiconductor device chips is decreased because circuit patterns on them are already completed.
Excessive grinding heat generated during grinding of a semiconductor wafer causes compositional deformation, grinding burn, 26 This drawback is well known in the art. It is also experienced that grinding heat is abruptly increased by abnormal grinding.
Therefore, in order to detect an abnormal grinding condition, a temperature of a wafer which is ground should be measured.
In this case, a thermocouple is brought into contact with a semiconductor wafer or is embedded in a grinding wheel to measure a temperature of the semiconductor wafer. However, it is very difficult to bring the thermocouple into contact with a semiconductor wafer. This is because a semiconductor wafer is formed of a very thin, fragile material and is ground while being rotated. Even if a thermocouple is embedded in a grinding wheel, a grinding temperature of a semiconductor wafer is indirectly measured. Therefore, a grinding temperature of the semiconductor wafer cannot be accurately measured.